Asphalt binder comprises four main fractions—asphaltenes (A), saturates (S), aromatics (A), and resins (R)—referred to as “SARA”. Asphaltenes plays an important role in determining the linear viscoelastic behavior of asphalt binders. In this research, asphaltenes are added as a distinct modifier to improve the performance properties of asphalt binder. The modified binders are aged using a rolling thin film oven. A dynamic shear rheometer is then used to measure the rheological properties of the binders at high temperatures. Changes in the chemical composition of the modified binders are also studied through the determination of SARA fractions, using precipitation and gravity-driven chromatography methods. The rheological results show that asphaltenes improve the stiffness and elasticity of asphalt binder. It is also shown that the addition of asphaltenes raises the high Performance grade (PG) temperature of the asphalt binder, with every 6% of asphaltenes added resulting in a one-interval increase in high PG temperature grade. SARA analysis shows that the increase in polar fraction content due to the addition of asphaltenes causes the stiffness, elasticity, and viscosity of asphalt binders to increase. The results indicate that asphaltenes are an effective yet inexpensive additive to improve asphalt binder properties at high temperatures.
In this study, high, intermediate and low temperature properties of two crude oil asphalts and three asphalts derived from Alberta oil sands bitumen distilled at temperatures of 400 °C, 430 °C and 460 °C were evaluated. High and intermediate temperature properties of the asphalt binders at different distillation temperatures were studied using a dynamic shear rheometer (DSR) through the performance grading (PG) tests. Low-temperature properties and performance grading were evaluated using a bending beam rheometer (BBR). The DSR high-temperature analysis indicated that oil sand bitumens distilled at high temperatures have significantly higher stiffness and more resistant to permanent deformation. BBR test results showed that irrespective of the asphalt source, oil sand bitumens distilled at lower temperatures are more resistant to cracking at low temperatures. The overall results indicate that oil sand bitumens are thus suitable to be used for both asphalt pavements requiring low and high-temperature resistance.
High strength, extended fatigue life, and improvement in rutting resistance are the main advantages of using high modulus asphalt concrete as a base course material in the pavement structure. The primary goal of this paper was to investigate the performance properties of the high modulus base course using different asphaltenes-modified binders. A crude oil binder and two different asphalt binders from Alberta oil sands sources were used to prepare the mixtures. To prepare hard-grade asphalt binders, all binders were modified using asphaltenes, a waste byproduct of the deasphalting of Alberta oil sands. The performance grades of the modified and unmodified binders were determined, and a mix design was developed for the high modulus asphalt concrete mixes. To evaluate the performance properties of high modulus asphalt concrete mixes composed of unmodified and asphaltenes-modified binders, Hamburg wheel tracking, dynamic modulus and flow number, and indirect tensile strength at low temperature were conducted. The high-temperature performance test results, including Hamburg wheel tracking and flow number tests, indicated that asphaltenes-modified mixtures show higher resistance to permanent deformation. However, the indirect tensile strength test results at low temperature showed higher tensile strength and lower fracture energy for the asphaltenes-modified mixtures compared with the unmodified samples. Moreover, according to the dynamic modulus test results, the asphaltenes-modified mixtures exhibited higher modulus values (stiffness) than the unmodified samples at different loading frequencies compared with the unmodified samples.
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